Some areas are very easy to route through when you want to stay on pavement, go anywhere you find a road, aka northern 2/3rds of Ohio...everything is paved. KY is much the same way, while MN is quite the exact opposite(if not on a highway or in town plan on being on gravel). I've been doing the 20th or 30th route plan for this years trip since it keeps changing with passing week as to what I'm going to do and my most recent routing has kinda surprised me with the amount of non-highway miles that are paved. The area in question, especially the western side of the area I would have figured would have been mostly gravel and I haven't found a gravel road in the area yet looking at streeview.

I'm wandering, and figuring this is region to region, aka in some case state to state, like Ohio, but in other places it may be just part of a state that has tons of gravel while other parts are pretty much all paved roads. It makes the planning much simpler when you have a pretty decent idea ahead of time which to expect. I realize you can use streetview to get the google car view of the roads in question but that still takes time and I'm looking for the 'sneak' tips to make it even quicker for coming up with routes without having to jump over to streetview.

Outside of incorporated areas(towns or cities) and off of the highways are their any areas/regions that quite well known for either or predominantly gravel or predominantly paved...and where are those areas?